Adiponectin (also referred to as GBP-28, apM1, AdipoQ and 30-kDa adipocyte complement-related protein (Acrp30)) is a protein which in humans is encoded by the ADIPOQ gene and is secreted by adipicytes (fat cells). It is involved in regulating glucose levels as well as fatty acid breakdown.
Adiponectin is the second best known adipokine, but in contrast to leptin, has several beneficial and protective effects. These effects include anti-inflammatory, vasculoprotective and anti-diabetic effects. Adiponectin is a 247 amino-acid protein monomer which forms trimers which further polymerize into larger polymeric complexes varying in size between 180 kDa (hexameres; LMW) or 400-600 kDa (16-meres; HMW).
Levels of adiponectin in human blood are between 5-15 μg/ml and are decreased in subjects with insulin resistance and type 2 diabetes. In general woman have a higher adiponectin plasma concentration (10-12 μg/ml) than men (7-8 μg/ml). It was also shown that adiponectin-deficient mice display diabetes. Moreover, adiponectin has been shown to promote insulin sensitivity in experimental models. Administration of adiponectin causes glucose-lowering effects and ameliorates insulin resistance. It is therefore beneficial to increase the level of adiponectin in human blood.
It has surprisingly been found that peptides selected from a casein hydrolysate activates adiponectin.